A quick-tempered person can be described as bizzoso in Italian. From the text, you learn that Geppetto is more than bizzoso; he is bizzosissimo: extremely quick tempered.

Geppetto loses his temper if someone calls him Polendina. Guai a chiamarlo Polendina!Look out if you call him Polendina!

Guai a is used to communicate danger, a threat.

Guai a criticare il governo.Look out if you criticise the government.Do not dare criticise the government.Beware if you criticise the government.

Guai a chi mi sfida.Beware if you provoke me.Look out if you provoke me.
You will be sorry if you provoke me.

Guai is the plural form of guaio, meaning trouble. More literally, then, guai a chi mi sfida meas something like trouble(s) to (he) who provokes me.

Whenever Geppetto was called Polendina, diventava subito una bestia(he immediately became a beast). Be sure to pronounce subito(immediately) with the stress on the first syllable. When Geppetto lost his temper, non c’era verso di tenerlo(there was no way to hold him back).Non c’è verso means there is no way, it is impossible.

Non c’è verso di convincerlo.There is no way to convince him.

Non c’era più verso di trattenerlo.There was no longer any way to hold him back.

Geppetto asks Mastr’Antonio (you will remember that this is the name of the falegname) what he is doing sitting on the ground: che cosa fate costì per terra?(what are you doing there on the ground?).Costì is a Tuscan usage meaning lì, or there.

Remember, Geppetto and the falegname address each other using the voi form: che cosa fate?(what are you doing?).

una formica

The falegname jokes that he is on the ground because he is busy teaching the ants arithmetic: insegno l’abbaco alle formicole(I am “teaching the abacus” to the ants). The Italian word for ant is formica.Formicola is a Tuscan variant. Both formica and formicola are pronounced with the stress on the second syllable: formìca, formìcola.

Buon pro vi faccia, replies Geppetto. This expression is used to convey good wishes to someone, along the lines of may it do you good. The expression is used sarcastically by Geppetto, however — Mastr’Antonio is clearly not teaching any ants anything at all.

Pro is a masculine noun meaning pro, benefit.Faccia is the third-person singular, congiuntivo presente conjugation of fare; it translates here as may it do.Buon pro vi faccia, then, literally means may it do you good benefit.